Packaging rpm (#260)

docs/packaging/build-rpm.md

+# How to Build the Duniter RPM Package
+
+1. Install dependencies:
+   ```sh
+   # Fedora
+   sudo dnf install clang cmake protobuf-compiler openssl-devel
+   ```
+2. Compile the project:
+   ```sh
+   cargo build --release
+   ```
+3. Install `cargo-generate-rpm`:
+   ```sh
+   cargo install cargo-generate-rpm
+   ```
+4. Build the package:
+   ```sh
+   cargo generate-rpm -p node
+   ```
+5. The `.rpm` package will be located in the `target/generate-rpm` folder.